The above images are a collaborative effort of Wendy
Carlos and myself. See her Eclipse
page for a description of her work.

The NEWKIRK
camera which Jonathan Kern designed
and built to obtain these images uses a 4" quartz/fluorite doublet of 60.25"
f.l. fed by an 8" quartz coelostat. Below are unprocessed exposures obtained
through the radially symmetric, neutral density filter located in the focal
plane which compensates for the steep decline in coronal radiance with
increasing distance. (the NEWKIRK filter, after Gordon Newkirk, former
director of the
High Altitude Observatory).
It is fabricated by evaporating a metal
film onto glass in a high vacuum. The basic requirement of such a filter
is that it compensate as accurately as possible for the radial decrease
in brightness as one goes away from the limb of the sun in the film plane
of the telescope. Thus, the transmission should vary as the reciprocal
of the function describing the K+F+sky brightness. This calls for an optical
density of 10 -3 at the limb (10 f/stops, or a factor of 1000)
decreasing very rapidly to a density of near unity at 4 solar radii. (See
curve) The solar image at focus was .570" in diameter. The plate scale
is .0175"/ minute of arc, yielding a photographic field of 2.12 by
2.68 degrees on 120 format roll-film (image size 2.23" x 2.81") . The central
spot you see in each image is the calibration window, which remains centered
on the sun. Because there is perceptible motion of the moon with respect
to the sun, the NEWKIRK filter may appear uncentered. It is not. These
images are also side-reversed, because of the single reflection introduced
by the coelostat mirror.